Slowly brown the ground beef over low heat, using a wooden spoon to chop and smoosh the meat, keep it very fine and smooth. When the beef is brown, drain the fat. Add the refried beans and use the wooden spoon to smash the whole beans into the mixture, creating a smooth texture. Add the salt, chili powder, and 2 tablespoons of the taco sauce to the mixture; remove from the heat. In another skillet, heat 1/4 inch of oil until hot (test with a small piece of tortilla, it should bubble when dropped into the oil). Spread 1/12 of the beef mixture on the center of each corn tortilla. Fold the tortillas over and press so that the beef filling acts as an adhesive and holds the sides together. Drop each taco into the pan of hot oil and fry on both sides until crispy. When cooked, remove the tacos from the oil and place them on a rack or some paper towels until they are a little cooler. Pry open each taco slightly; add 1/2 slice of American cheese (cut diagonally) and some lettuce; top with about 1 1/2 teaspoons of the remaining taco sauce.